The news on Friday that Justice Ruth Bader Ginsburg had died, creating a vacancy that could reshape the Supreme Court for a generation, revived talk about an idea that has been bandied about for years but, until recently, not feasibly considered by people in a position to enact it: court packing.
The term is commonly associated with President Franklin D. Roosevelt, who pushed legislation in 1937 that could have expanded the Supreme Court from nine to as many as 15 justices. The history is more complicated than the usual narrative suggests: Mr. Roosevelt, aiming to push older justices to step down, wanted to add a justice to the court for each sitting justice who refused to retire after 70.
More than eight decades later, the idea of expanding the court is back. In 2016, Senator Mitch McConnell, the Republican leader, refused to hold a Senate vote on Merrick Garland, who was nominated to the court by President Barack Obama after the death of Justice Antonin Scalia. Mr. McConnell held the seat open until after the inauguration of President Trump, who nominated Justice Neil M. Gorsuch.
Mr. McConnell’s move led some Democrats, including the presidential candidate Pete Buttigieg, to suggest expanding the court. They argued that Republicans had “stolen” a seat that should have been filled by Mr. Obama, and that Democrats would be justified in adding seats to shift the ideological balance back.
Republicans have called the idea radical and undemocratic, and some Democrats have feared that it could backfire. The Democratic presidential nominee, Joseph R. Biden Jr., rejected the idea last year, telling Iowa Starting Line, “No, I’m not prepared to go on and try to pack the court, because we’ll live to rue that day.” He did not address the subject on Friday.
Mr. McConnell’s declaration on Friday that the Senate would vote on Mr. Trump’s nominee to replace Justice Ginsburg — a reversal of his 2016 stance that the nation’s voters should choose a president first — added fuel to the fire, with progressive activists and at least one senator calling publicly for court packing. Their premise, spoken in some cases and implicit in others, was that if Republicans had dispensed with the usual rules, Democrats would be justified in doing so, too.
Senator Edward J. Markey, Democrat of Massachusetts, tweeted on Friday night: “Mitch McConnell set the precedent. No Supreme Court vacancies filled in an election year. If he violates it, when Democrats control the Senate in the next Congress, we must abolish the filibuster and expand the Supreme Court.”
Although the Supreme Court has consisted of nine justices for well over a century, the Constitution does not require that number, and Congress changed the size of the court several times between its establishment and the Civil War.